I use melatonin, along with valerian root sometimes. they wont knock your ass out like some drugs will, but you wont become addicted either.
ive used GHB, and valium, and xanax. but i went down hill from there, started takin them to sleep, then relax, then to party, and then before work, and at work, and after. i started drinkin heavily, and everything. it was hard to quit, very hard, but ive cut them all out, beer and all. bodybuildin/powerlifting has saved me.
anyways, point is, stay away, that shit is addictive, and yeah, some can control it, but its so easy to loose control.
for sleep, stick to somethin mild, and non addictive.